1. Technical Field
The present invention relates to the technical field of an onboard battery that is mounted in a vehicle such as an automobile and can be used even in a cold area.
2. Related Art
In various vehicles such as an automobile, an onboard battery for supplying electric power to a motor and various electrical components is mounted.
In recent years, vehicles such as, in particular, electric vehicle (EV), hybrid electric vehicle (HEV), and plug-in hybrid electric vehicle (PHEV) are becoming pervasive, and an onboard battery having a high power storage function is mounted on these vehicles that use electricity as power.
The onboard battery is constituted by a plurality of battery modules, and the battery module is constituted by, e.g., a battery stack in which each of a plurality of battery cells (secondary battery) such as a nickel-metal hydride battery and a lithium ion battery and a separator disposed between the battery cells for securing a cooling path are alternately stacked on each other, a fixing member that fastens the battery stack in a stacking direction, a bus bar module that electrically connects the battery cells to each other, and a chamber that sends cooling air to portions between the battery cells.
The output performance of the batter cell used in the onboard battery described above changes depending on temperatures, and the output performance of the battery cell is reduced when the temperature is low. Consequently, with regard to the onboard battery used in a cold area, there is a possibility that sufficient electric power is not supplied to a motor or the like from the onboard battery when the temperature is low such as during winter season and an output required in the motor or the like cannot be obtained.
To cope with this, some onboard batteries used in the cold area are provided with a heater, the battery cell is heated using the heater when the temperature is low, and the output performance of the battery cell is thereby enhanced (see, e.g., Japanese Unexamined Patent Application Publication (JP-A) No. H11-176487).
In the onboard battery described in JP-A No. H11-176487, tubular cell accommodation units are provided in an accommodation case, and the battery cell is inserted into and disposed in each cell accommodation unit. A heater (Peltier device) is inserted into and disposed in a gap formed between the cell accommodation units, the heater is driven with a current supplied thereto when the temperature is low, and the battery cell is heated using the heater.
However, in the onboard battery described in JP-A No. H11-176487, the battery cell is disposed inside the cell accommodation unit and the heater is disposed outside the cell accommodation unit, and hence the cell accommodation unit is present between the battery cell and the heater and the efficiency of heating to the battery cell by the heater may be reduced.
In addition, the battery cell and the heater are positioned inside and outside the cell accommodation unit so that the weight of the battery cell is applied to the heater as a load via the cell accommodation unit, and thus damage to the heater may occur. In particular, the weight of the battery cell may be applied to the heater as a large load via the cell accommodation unit due to vibrations generated during running of the vehicle.